In general, there are two complementary approaches to manufacture an object: additive manufacturing and subtractive manufacturing.
Additive manufacturing involves aggregating material to form the desired object. In contrast, subtractive manufacturing involves removing material to form the desired object. In practice, many objects are manufactured using a combination of additive and subtractive techniques.
A form of additive manufacturing—colloquially known as “three-dimensional (3D) printing”—is the subject of intense research and development because it enables objects with complex geometries to be manufactured without molds or dies. Furthermore, 3D printing enables the mass customization of objects with different dimensions and characteristics. There remain, however, many challenges in the design, manufacture, and use of 3D printers.